The Scientific Method
by valonqar
Summary: She was logic where he was emotions. She was uptight where he was free. She was muggleborn where he was pureblood. She was Lily, and he was James, and with the meddling of their friends and the help of a little bit of maths, they're finally going to end up where they belong: with each other.
1. Prologue: Determination

**A/N: so I'll just come right out and say it: this is heavily inspired by the premise of An Abundance of Katherines, but the plotline is **_**completely **_**different. If you've read the book you'll know what I mean, I just want to give John Green the credit he deserved for the formula - that part was him!**

**Everyone loves Jily. Read, maybe review if you want, and enjoy!**

**xx**

"You're mental."

"Wrong. I'm _brilliant._"

"No, Lils, you're_ mental_. Off your rocker, barking like a dog, lost every marble in the bag level of mental. I mean, I always knew you were a _logic-before-emotions_ kind of person, but this..." Amelia scrunched up her nose as she gave her red-headed friend a sceptical look. "This is just bloody _weird_."

_Yeah, that was about the reaction she had been expecting_.

Honestly, Lily didn't see what was so strange about the whole thing. After all, wasn't there some kind of study going around where scientists were trying to prove that love was a chemical reaction in the brain, not even a tangible _thing_ at all? Of course, these _were_ wizards she was dealing with - sure, transfiguring an animal into a water-goblet made _complete_ sense, but as soon as you tried to talk chemistry with them they blanked out.

"It's not weird, it's _scientific_," she shot back with a confident grin, ignoring the confused look, one slightly resembling an owl with a head injury, that her friend sent her way. _Purebloods. _"I'm telling you, I've _done_ it! The perfect formula for determining not only the length of a relationship, but who will break up with who, who's more likely to cheat, and who'll fall the most in love. It's bloody flawless!"

Looking like a niffler who has just stumbled upon a pot of gold, Lily waited patiently for Amy to finally catch onto the brilliance of the whole thing. She would be famous! Lily Evans, _muggleborn _witch, would be famous for creating the first-ever device that would be able to predict the course of a relationship entirely, even one that hasn't even _happened_, from it's start date to it's end, from who loved who the most to who would break up with who, _everything_ would be there.

And when she was world-renowned as a genius, with her Order of Merlin, First Class just one of her many honorary titles, she would rub it in the faces of all the nay-sayers, starting with one Amelia Darville.

"It's never going to _wooork,_" Alice Longbottom sing-songed from the other side of Amy, and the red-head scowled. Traitors, the lot of them! "You just don't get it because you refuse to fall in love, Lils. I mean, it's not _your _fault you're a robot, but the lot of us humans would be happy to tell you that you can't just _predict _love. There's too many factors, and emotions change all the time. A little thing called hormones; heard of them?"

Bloody bints thought they were so _clever._

_"_Alice, do you honestly think I haven't taken all that into consideration?" With a roll of her eyes, Lily tore the formula sheet out of her bag with a flourish and passed the parchment to her two friends, displaying it proudly for them all to gawk at. "Voila! It takes into account the gender of each person, age, height, attractiveness - on a general scale of one to ten, the value of which can be determined using the seperate formula found _here..."_ Pointing to the spot on the sheet where the smaller equation was scrawled, Lily couldn't help but grin at their gawking expressions. _Score one for mathematics. _"Punch in all the variables, and you've got yourself a foolproof equation for love."

"What _is _all this rubbish?" Amy breathed, sounding almost afraid, as Alice simply continued to stare in horror. _Purebloods, purebloods, purebloods. And they think I'm mental._

"That, my dear friends, is maths. And it's one hundred percent accurate...so long as you don't make a mistake punching in your numbers, that is."

There was no way they could question her now - not when she had presented them with such solid evidence, evidence that they weren't even smart enough to understand. How could you argue something you didn't get, something _you were afraid of_? Of course, she didn't say that outloud as she knew just what their retaliation would be - then how could she argue _love_? - but it was entirely different.

Different because she had _science_ on her side, and all they had were rotten emotions. Emotions that were good for nothing and only got the brain all muddled up and confused. Confusion was a genius' worst enemy, and Lily _was _ a genius, or at least she would be once she was proved right.

"You gotta prove it," Alice said suddenly with a mischievous smile, giving Amy one of her _just-you-wait _looks before turning her gaze back to the redhead. "And not with me and Frank, because that's just not fair. No, you gotta prove it with _you_ and someone. You gotta date someone that Amy and I choose, and we'll put in the numbers without letting you see - before you can argue, _yes_, I know how to do maths. And then you'll have to commit yourself to a relationship with that person, and if it follows whatever pattern these formulas spit out for us, then we'll admit that you were right. But you can't know the answer, or it'll mess with the results."

_Hm...well, it was tempting_. But Lily didn't really know if she trusted Alice and Amy with something as massive as her finest work - no, she would have to raise the stakes, at least a little bit.

"Admitting I'm right isn't enough - I already _know _I'm right." Huffing, Lily crossed her arms over her chest and stared the two down, trying to find an appropriate punishment for them, while still being a reward for herself. "You gotta admit it to the entire school, not just by _announcing it_, but by announcing it _and _being my assistants for a week. Write my essays, help with my potions, anything I do you have to contribute to with one hundred percent effort."

The two both looked like they might be sick, but after a silent conference Lily was pleased to see that they would take her up on her challenge. _Wonderful_. Now all she had to do was find an appropriate guy to "date", one whose company she actually enjoyed - because she wouldn't be able to tell him about the formula, but at least she could have a not-miserable time with him. That would work, wouldn't it?

"How about Remus?" she asked hopefully, eyes falling on the sandy-haired boy in the corner of the library. "He's perfect! Sweet, gentle, smart, it'd be _brilliant!_"

But Amy and Alice were both full-on smirking now, and a sinking feeling began to emerge in the pit of Lily's stomach. _They wouldn't_. There was no way her two best friends in the would would be so cruel, so heartless that they would make her...no, it was impossible.

"Not him," she begged before she could stop herself, green eyes wide as she thought of the shaggy-haired devil of her co-head, the bloke who had been ruining her life for seven years straight. "Not him, you _can't_, that's just plain evil! I won't do it, I _won't_, you can't make me...please don't make me!" Didn't they have hearts? Didn't they have _souls? _Couldn't they feel the slightest bit of compassion for her, their best friend, when she was so clearly upset?

But no, apparently they couldn't. Looking absurdly pleased, the two were grinning at her with expressions that could only be described as immensely satisfied.

"James Potter," Amy stated matter-of-factly, although her smirk betrayed her business-like tone. "You, Lily Evans, have to not only agree to go on a _date_ with, but agree to be in a _relationship _with James Potter and let it ride out it's course naturally. Then, _only then _will you be able to prove your stupid formula right."

She couldn't.

_But she had to_.

It was mental.

_But it was for science!_

"Fine," she growled, snatching up her books as she stood, glaring at the two tittering witches across from her. "But we'll see who's laughing when you're both cleaning up my _accidentally _spilled potions in class after I've made you both look like idiots!" Storming out of the library in a huff, Lily ignored the giggles of her friends, even as she could still hear them out in the corridor.

Oh, later they would see who got the last laugh.

_But first, she had a Marauder to catch._


	2. Impossibilities

**A/N: Thank you for the lovely reviews! For this chapter I'm hoping to get at least the same amount before I continue, so everyone who reads, PLEASE try and review!**

**xx**

There were many ways in which Lily had heard James Potter described.

_'Dreamy,' _she had heard the more pathetic groups of girls swoon. _'Handsome. Charming. Clever.' _Now, handsome she could grant them, as painful as it was for her to admit, but _charming_? _Clever? _She didn't think she had heard Potter be remotely clever in his life, and if making constant fart jokes with Sirius Black and throwing pastries at first years was _charming_, then all the romance novels she had read (purely for research's sake, of course) had completely misinformed her.

No, James Potter was neither dreamy, nor charming, nor clever, nor any other adjective of the complimentary sort. Rather, he was an _arse_, and that was all there was to be said about that.

It certainly didn't help her viewpoint of him that the main, pathetic ways he tried to win her over all involved pulling pranks on her classmates in a foolish attempt to make her laugh. Did he seriously think she would find giving Frank Longbottom a wedgie _romantic_? In their first years together she had found the ponytail-pulling mildly annoying if anything, but the constant pranks and lame puns were now just _infuriating_.

_Although_, Lily allowed herself to ponder for a moment, _he can be romantic if he tries. Remember that time he got you the box of chocolate frogs and charmed them all to jump and spell out your name with a heart?_

Of course, he had ruined it moments later by hanging Severus from a tree.

_Typical Potter_.

And now she was on her way over to him, not to yell at him or scold him or roll her eyes at his foolish antics, but rather to ask him on a date. A ruddy _date_ with James Potter, and not just one date in the hopes that he would leave her alone, but a date-date, and if she abided by Alice and Amy's rules, it would be the first of many to come.

They had been exceptionally specific in their rule-making for the bet, having cornered her in their dormatory after Lily had had no success locating the Marauder - something about quidditch practice, Remus had muttered before running off towards the forest, although she was certain he lying about _something_ - although that didn't surprise Lily in the slightest. Amy had taken the lead, and Lily _swore_ the brunette liked to see her suffer.

_"No sabotaging this relationship on purpose. It's gotta happen like you want it to happen, and you gotta act like yourself. Otherwise, you're tampering with our results, and that's not very science-y at all." Amy's dark eyes bore into hers with ferocity, and were it anyone else Lily would be shocked at their passion. But after it had been decided that if Lily was wrong she would have to buy whatever her two friends wanted from Honeydukes without complaint, the over-competitive witch had sprung into action and was no writing down a list of rules the length of the table they were seated at._

_"Also, you can't say a word to him about the bet." It was Alice's turn to pipe up, less intense than Amy but equally as excited. "Not a single word, because that's not very science-y either."_

_"This is absurd," Lily muttered under her breath, trying her hardest not to just call the entire thing off. Was dating Potter _really_ worth proving the greatest work of her life so far right? For some reason, she was beginning to think it wasn't. "I mean, he's going to know something's wrong. I hate him, and everyone knows that! How in Merlin's name am I supposed to convince him otherwise?"_

_The two shared a secret smile, one that made the red-head's stomach drop, and she knew that whatever the two of them had in store for her, it wasn't going to be fun in the least._

_But she couldn't concede. Not now, not when she had so much to lose._

_Which is why she took the parchment they offered her without a word of complaint, not even flinching as she read it over once, twice, again, not even as the bile rose in her throat and she began to feel a touch...well, a lot faint. _

_"You two don't stand a chance."_

However, as she stalked towards the form of the laughing boy sitting under the tree, the words on the parchment memorized perfectly, Lily was feeling as if she should eat her words. How _could_ she do this? She wasn't an actress, and she certainly wasn't a _romantic_. How on earth was she to convice a boy that she loved him, or even _slightly _enjoyed his presence, when she couldn't even convince herself?

But the time to fret was over, because now she was standing directly in front of him, and he was staring at her, and Sirius and Remus had stopped whatever bizarre game of tag they were playing to _watch_, and she was feeling a little bit like running away was the best possible option.

Before he could say a single stupid thing to her, however, she was already blurting out the words that she could never imagine herself saying, not in a _million_ years, and especially not to James bloody Potter. "I've been having a long think about things, and I figured it was about proper time I told you the truth about me." Stopping herself at the look of sheer confusion in his eyes, Lily allowed herself a moment of hope before adding. "That is, if you want to hear it."

_Please say no please send me away please say you've got a girlfriend and her hair is redder than mine and she's got greener eyes please. Say. No._

And so, as was suited to her luck, he responded with, "I'd happily listen to any word that comes from that delicious mouth of yours, Evans."

_Of course._

Fighting desperately against the urge to smack him across his infuriatingly gorgeous face, Lily took a deep breath to calm her shot nerves. She could do this, _no, _she _had _to do this. It was the only way she could confirm to the rest of the world what she already knew - not only that she was a genius, but that love was predictable, and she knew _just how _to predict it. It was the only way, and it was the only choice she had left.

And so she repeated those words in her mind as she continued on, feeling slightly more confident as she saw her goal coming ever-so-slightly closer to her reach. _Fake it 'till you make it, Lils. Isn't that what they say? Fake it 'till you make it. _"We'll, I thought you should know that...that I've been madly in love with you since the first time I saw you, and all these years I've just been too scared to say anything. Because," Oh _Merlin, _this was literally causing her physical pain to say, but she pushed on, faking the pause for nerves as she gave a wide-eyed James a shaky smile. "You're just so _handsome_ and I never thought I stood a chance but now...now I was hoping we could maybe, you know, give it a go? Something like that?"

_There_. She had said the gist of what Amy and Alice had written for her, and that would have to be good enough. Except...except James wasn't saying a thing, just _staring _at her, and Remus and Sirius were dead silent - probably for the first time _ever_, in Sirius' case, and her face was starting to heat up and her palms were getting clammy and _why wasn't he saying anything_?

And then he standing up, and then he was kissing her, _really_ kissing her, and Lily thought that that must have been an answer.

_Oh_.

She knew she had to play along, _had_ to respond, but her hands seemed frozen at her sides, her eyes stuck wide open in pure and simple shock. This...she hadn't been expecting _this._ Maybe a little peck, a hug, preferably a friendly handshake, but _this? _This was a kiss filled with the need that a man lost in the desert had for water, or that a giant squid had for a black lake.

This...this...

_This actually isn't half bad_.

Before she knew it, before her rational mind could make her see sense, Lily realized that she was kissing him back, not with the same passion or force, but simply because it felt _nice_, and although logic usually took up the forefront of her mind, Lily Evans was not in the business of denying herself nice things - even if that nice thing _was _locking lips with the person she hated more than peanut brittle.

Dimly she realized that there was hooting and cat-calls in the background, and it took Lily a moment to realize that those weren't just coming from James and Sirius. _No, _those were coming from a _crowd,_ and as she pulled back from Potter with a gasp she felt her cheeks flushing redder than her hair. What on _earth_ had come over her? Perhaps it was just the fact that she hadn't been kissed many times in her life before - hardly ever, actually - and she was sure Potter had kissed so many people that he was basically a certified professional by now.

So clearly that explained all of it; one of her first kisses had been a bloody good one, and she had gotten carried away. Carried away and nothing more, and she knew that for a fact because as soon as she looked upon Potter's widely smirking face as he let out a cheer, what she was feeling _certainly_ wasn't love.

Not even close.

As the crowd finally faded along with her flush, Lily turned to the boy with an innocent smile that she had practised in the mirror many times earlier that day - one of the _'flirty_' facial expressions that Amy and Alice had trained her in. "So..." and she tried to think of something clever or cute to say before coming up completely and entirely blank. Because what was one meant to say to someone after she had professed her love to him and then had the living daylights snogged out of her? _'Hey, thanks for the snog, see you around?' _For some reason she didn't think that was the best choice.

"So," he replied, and although his traditional cheeky grin was clear on his face she could tell that he was a little lost for words too - likely for different reasons that her, of course, but it was always nice to know that she wasn't alone in her discomfort. But then his cheeky grin grew and his cocky composure was back, and Lily cursed herself for hoping that maybe, for a moment, Potter could actually be _normal_. "You're _madly _in love with me? Shame you didn't tell me sooner - we've got _years_ of snogging to make up for."

_He had better be joking_.

Although, for _some_ reason, she didn't think he was at all.

_Brilliant._

Meanwhile, on the other side of the castle, two brunettes sat huddled in the Gryffindor girl's dorm room, wide eyes desperately scanning a sheet of parchment filled with numbers for any, _any _possible mistakes.

"But it can't be!"

"Are you sure you added everything right? You're not very good with numbers and..."

"_Yes_ I'm sure, Alice! Merlin, I'm not an invalid - I _do_ know how to do _some_ math."

"But...but..." Alice stared at the paper some more, trying to tune out the mutterings of the girl next to her as she focused on the numbers. Even though she was a pureblood she had a good enough understanding of maths to use a formula - granted, Lily's so-called _'love equation' _wasn't the simplest of things, but she figured she could work it out it well enough, once the graphs were all plotted and the numbers all sorted.

And she had a good enough understanding of Lily to know that the results on the sheet of parchment made absolutely _no sense whatsoever._

"There's something wrong." Alice finally stated matter-of-factly. "Lily was wrong with the formula, we've proven her wrong already. We can just show this to her and she'll call the whole thing off and we'll have won, simple as that! She was wrong, and this is our proof."

Amy mulled it over for a moment, shaking her head quickly. "_No_. We're going to win anyways, right? It's funnier to watch her suffer in the meantime." With a wicked grin spreading over her face, Amy snatched the parchment out of her friend's hands and shoved it in the trunk beside her bed. "But we have to keep this hidden. Lily _can't know_, do you understand? We'll let the whole thing run it's course, make her squirm, and _then_ we'll win. Not now."

But even as they tucked the parchment away, neither of the two girls could forget what they had seen. It was wrong, right? It _had _to be wrong. There was no other option.

Because when they tried to calculate how long the relationship would last, the number went on...forever.

And if there was one thing they knew, it was that when it came to Lily Evans and James Potter, _forever _wasn't even close to an option.


End file.
